ul {
  width: 100%;
  overflow-x: auto;
  list-style-type: none;
  display: flex;
  position: fixed;
  top: 0;
  left: 0;
  z-index: 1000;
  background-color: #fff;
}
ul li {
  position: relative;
  text-decoration: none;
  margin: 0 5px;
  padding: 5px 0;
  white-space: nowrap;
}
ul .active {
  color: red;
}
ul .active::after {
  content: "";
  height: 2px;
  width: 100%;
  background-color: red;
  position: absolute;
  top: 90%;
  left: 0;
}
